Field
Embodiment described herein relate to micro devices. More particularly embodiments relate to a compliant electrostatic transfer head array and a method of transferring micro devices to a receiving substrate.
Background Information
Integration and packaging issues are one of the main obstacles for the commercialization of micro devices such as radio frequency (RF) microelectromechanical systems (MEMS) microswitches, light-emitting diode (LED) display systems, and MEMS or quartz-based oscillators. Traditional technologies for transferring of devices include transfer by wafer bonding from a transfer wafer to a receiving wafer. Such implementations include “direct printing” and “transfer printing” involving wafer bonding/de-bonding steps in which a transfer wafer is de-bonded from a device after bonding the device to the receiving wafer. In addition, the entire transfer wafer with the array of devices is involved in the transfer process.
Other technologies for transferring of devices include transfer printing with elastomeric stamps. In one such implementation an array of elastomeric stamps matching the pitch of devices on a source wafer are brought into intimate contact with the surface of the devices on the source wafer and bonded with van der Walls interaction. The array of devices can then be picked up from the source wafer, transferred to a receiving substrate, and released onto the receiving substrate.
In another implementation, the technology for transferring of devices is enabled by an array of electrostatic transfer heads as described in U.S. Pat. No. 8,415,767. As described, an array of electrostatic transfer heads may be formed from a silicon-on-insulator (SOI) substrate. Furthermore, the array of electrostatic transfer heads may be made compliant such that each silicon electrode is deflectable into a cavity between a base silicon substrate and the silicon electrode. In this manner, each compliant electrostatic transfer head can compensate for variations in height of the devices during the transfer process.